The present invention relates generaly to the field of paper feeding machines, and more particularly to an adjustable pressure roller assembly for maintaining proper feeding pressure on various types of paper and paper assemblies between a feed roller and a backup pressure roller, including the application of no pressure at all.
The present invention was conceived, designed and developed in connection with the development of various improvements in a high volume mailing machine, but it has since become apparent that the utility of the invention is not limited to the application for which it was originally intended, but rather extends beyond that as discussed further below. For the purpose of illustration, however, the invention is herein disclosed primarily in connection with mailing machines for which it was originally designed.
Most high volume mailing machines typically comprise an envelope storage and feeding module in which a stack of envelopes is placed in a hopper with the flaps of the envelopes lying in an open position, and from which they are fed one at a time into the mailing machine for further processing. The storage and feeding module also includes a moistening device which applies moisture to the gummed surface of the envelope flaps as they move along a feed path. The module further includes a flap closing device which has appropriately shaped guide surfaces for gradually closing the envelope flaps after they have been moistened, although this guide does not normally close the flaps sufficiently far to effect a seal between the flap and the rear surface of the envelope. In many mailing machines, the envelopes are then fed between a pair of rollers which apply a fixed pressure to the flap to cause it to seal to the envelope. In some mailing machines, the pressure required to seal the envelope is provided merely by a vertically movable platen which presses the envelope against a printing die to cause a postage indicia to be printed on the envelope.
In either event, certain problems have developed as mailing machines have increased in speed of operation and in the variety of types of envelopes which can be accommodated by the mailing machine. One problem has been that if the pressure rollers are set to apply sufficient sealing pressure for normal mail pieces having from one to three or four sheets in the envelope, they will apply excessive pressure to very thick envelopes (e.g. inch or more), thereby either damaging the envelope or its contents, or causing a jam in the mailing machine due to improper feeding. On the other hand, if the pressure rollers are set to apply normal sealing pressure for thick envelopes, they will not provide sufficient pressure to cause an effective seal between the flap and the back surface of the envelope. It has been found that there is a rather narrow range of sealing pressure that is required to effectively seal an envelope flap which is sufficient to squeeze out excessive moisture while not providing excessive pressure that may damage the envelope or cause a misfeed. Thus, it is desireable to have a pressure feeding assembly which is fully adjustable within the range of sealing pressures that will effectively accommodate all thicknesses of envelopes which may be normally processed through a particularly mailing machine.
Many other situations have been appreciated where it is desireable to have an adjustable pressure roller assembly in which the pressure applied to paper being fed betweeen two rollers can be adjusted or removed altogether. For example, with respect to pressure adjustment, in a paper feeding machine in which very thin or fragile paper is being fed, it can become critical to apply a proper amount of feeding pressure between a feeding roller and a backup pressure roller within a very narrow range of pressure in order to avoid the possibility of the paper being creased or otherwise mutiliated. Some forms of paper have very smooth or calendared surfaces, and others have very rough, almost blotter-like surfaces, each of which requires an appropriate amount of feeding pressure to avoid mutiliation or misfeed of the paper. In either of these cases, the use of a backup roller which is spring biased toward the feed roller with a fixed tension spring has been found to be inadequate in many situations where it is desired that the same machine accommodate different types or grades of paper at different times. Also, if it desired to feed multiple layers of paper through a machine, it is possible for excessive pressure to cause the layers to become misaligned by being forcibly squeezed through the roller assembly, or alternatively to become misaligned becuase the sheets are fed with insufficient feeding pressure between the rollers.
On the other hand, with respect to complete removal of feeding pressure, it often happens that a mailing machine is used in a non-printing mode for the purpose of merely sealing envelopes on which no postage indicia is being printed. One example if this type of operation is the sealing of envelopes containing pay checks of corporate employees which are then delivered by hand through the internal corporate mail distribution system. If a mailing machine is used in which envelope flap sealing is accomplished by application of a platen pressing the envelope against a printing die, it is apparent that the envelope will not be sealed if the postage printing assembly of the mailing machine is not used. Also, envelopes such as self mailers which are used for such forms as W-2s, jury notices, etc., which are sealed all around and are opening by separating one side of the envelope along score lines, do not have flaps that are sealed in the normal manner, and therefore do not require pressure sealing, thereby removing the potential for mutiliating the envelopes. Some of these envelopes have carbon on one side since they are addressed after the form is inserted, and excessive pressure from a pressure sealing assembly could cause an undesirable amount of carbon to transfer from the envelope to the form. It is thus apparent that there is considerable need over a broad range of utility for a simple and effective adjustable pressure roller feeding assembly as hereinafter disclosed and claimed.